1. Field of the Invention
The present invention relates to a surface and downhole system for the control, monitoring and operation of a single or multiple wells. The downhole portion of the system is entirely self contained and once in place requires no communications, power or control function to be provided from the surface. The surface portion of the system communicates by movable module with the downhole portion of the system. The surface portion of the system itself is remotely addressable via satellite line, microwave line, or via land line. If desired, various components of the modular system may be interrogated, evaluated, and/or replaced independently of the well completion and production schedule.
2. Brief Description of the Prior Art
Many oil and gas wells being drilled at the present time are drilled through and have multiple perforation and producing zones. Additionally, particularly in offshore field development, the use of multi-lateral wells drilled from a single central well borehole have become an accepted practice. Each production zone, or lateral well of a multi-lateral system, has its own set of operating parameters. These parameters of pressure and flow rate are determined by the physical characteristics of the reservoir rock and the borehole conditions at each production zone, or lateral well, such as permeability, porosity, formation pressure, formation gas content, formation water content, etc. In other words, in present day well completion practice, a single well borehole may comprise a series or set of different production parameters of flow rate and pressure wherein each member of the series of set requires its own separate handling logic to optimize its production of hydrocarbon. In a typical well each producing zone may contain oil, water and gas. It is desirable to produce the maximum possible rate.
In recognition of these completion practices well control systems utilizing microprocessor logic circuitry both at the surface and downhole have been developed. In such prior art systems, ultimate control of the operating system has always heretofore been maintained from the surface. For example, U.S. Pat. No. 5,132,904 discloses a well control system having a microprocessor to monitor well pressure levels, timed sampling limits and their combination. The sensors are connected by wire to the microprocessor at the surface in this system. Similarly, is the disclosure of PCT International Publication No. WO 96/10123 published Apr. 4, 1996 a surface microprocessor is connected by wire to downhole pressure and flow sensors in several different completion zones of a well. In U.S. Pat. No. 5,273,112 a surface controller communicates with a downhole instrument set for measuring pressure and flow via an annulus pressure modulation system which utilizes annulus pressure as a communication conduit to the downhole instruments.
In the cases where communications to the surface are performed by wire, special production tubing is required having communication and power wire and protectors therefor run along its length from the surface to the downhole tool. This wire is a weak link in the system, even using the best of available protection systems due to short term mechanical stress placed on it, for example during installation, and due to longer term stress placed on it due to lengthy timewise exposure to borehole temperatures, pressures and chemical activity. Similarly, in the case where tubing or annulus pressure modulation systems are used to control downhole tool settings, very heavy and bulky high pressure pumping systems are required at the well head to perform the communication function. Such pressure pumping systems may not always be available in remote location and when they are, their use can be very expensive.
Accordingly, it would be very desirable to have an entirely self contained downhole well monitoring and control system. Such a system would be even more desirable if it were repairable without decompleting the well. Decompletion (or the cessation of fluid production) is presently required for repair of known well control systems, such as those previously mentioned. Killing the well requires loading the well with fluids that made a higher hydrostatic pressure than the reservoir pressure. This requires that the well be "unloaded" (or the fluid removed) in order to begin production again. This is very expensive, time consuming and the fluids used may damage the formation permanently, inhibiting optimum production from the well.